And you've already been answered
@Phr3121 but no the "IRA" is not coming back, not the IRA as most people mean it...which is the Provisional IRA from the Troubles, which was a well-organised, well-supported and extremely effective organisation. That is what people typically think of when they think of the IRA. However, the Provos are not the only IRA....so in another sense the IRA is not coming back, because they never went away. Of course, that statement obviously requires a bit of historical exposition...
The original Irish Republican Army fought the militarised police force and British Army forces in the 1920s during the Irish War of Independence, they were originally known as the Irish Volunteers which was theoretically a regular army and was organised as such (in practice, they quickly changed to guerrilla tactics, some of the first examples of this in modern history during the war against the British). There was also an even older organisation called the Irish Republican Brotherhood (IRB) which dated back to the 19th century, this was a secretive oath-bound organisation which operated through attempted infiltration of other organisations and, in the 1880s, a dynamite campaign of bombing financial targets in England. The IRB and the IRA weren't the same thing, but there was overlap in the leadership. The IRB was a small, fraternal organisation which had little support by the end of the 19th century and the Volunteers/Old IRA was a huge organisation which eventually obtained mass support after the 1916 rising/1919 and the beginning of the war of independence.
After War of Independence a treaty was signed in which Ireland was declared an independent dominion (apart from the area of Northern Ireland...) within the Commonwealth, basically on par with what Canada, South Africa, Australia and New Zealand had at the time. Functionally independent but with some symbolic ties to Britain remaining (and in Ireland's case a few things like ports which would remain under British control for a time). Some though this would give Ireland a chance to eventually get total freedom (which was exactly what happened), others disagreed and wanted nothing but a fully independent republic with no symbolic ties to Britain at all...this led to the Irish Civil War. The majority of the original IRA became the official army of the new Irish Free State. Those who were Anti-Treaty became known as the "Irregulars"...they lost the civil war and were subsequently forced to become an 'underground' organisation in the decades that followed, operating much like the old IRB...little popular support, very secretive etc. They eventually became known as simply the IRA and it is from this organisation that all the modern "IRA's" are descended from.
This IRA continued to try and fight against the British forces in Northern Ireland (the so-called northern campaign in the 40s, and the border campaign in the 50s), as well as some bombs in Britain. Largely they were quite ineffectual and had very little popular support, but they kept the organisation going despite that. Over time the northern leadership of the IRA was becoming increasingly separate from the southern command (a result of the border between the Republic of Ireland and Northern Ireland). At the onset of The Troubles in the late 60's, the northern IRA split into two more groups....the Official IRA or 'stickies' (who were more heavily Marxist in their outlook and wanted to avoid sectarian divisions amongst the working classes), and the Provisional IRA. The Provos would become the much larger group and it was they who undertook the majority of the armed activity during The Troubles, when people talk about the IRA nowadays they are almost always referring to the Provos. It was the discrimination faced by ordinary Catholics/Nationalists at that time in Northern Ireland, combined with the repression by the British Forces (who were initially seen as protection from violent loyalists and welcomed) and the killing of Catholic civilians which laid the grounds for mass support once again (on a scale not seen since the period of the original war of independence).
Once the The Troubles ended and the Good Friday Agreement was signed there were some within the Provisional IRA who disagreed with peace and wanted to continue the fight, known as "Dissident Republicans". As you can see this is a recurring theme within modern Irish history....but they have
very low levels of popular support, and while obviously dangerous are much less sophisticated, much less well-trained and well-equipped than the provisional IRA...they go by various names - the Real IRA, the Continuity IRA, Óglaigh na hÉireann (a Real IRA splinter group) etc. These groups have membership merely number in the hundreds compared to the mass support (whether tacit or outright) of the provos. They continue to try and do things like kill policemen and security guards + explode devices but thankfully are almost always stopped by the security services.
This latest car bomb in Derry...well on an empty street clearly not the most successful attempt ever and extremely crude in comparison to Provos (who got better over time of course)....but still a bomb and if there were people on that street it would have been extremely dangerous. But, all this is to say that this is still the actions of a minority IRA splinter group....of which there have been a number over the years. The Provisional IRA were of a particular time and circumstances created by that time, things aren't going to suddenly do a 180 degree switch back to the Troubles. The vast majority want peace.