Siver DID take McGregor down, anyone who watched the fight saw that, it doesn't matter if they "technically" don't count for whatever dumb reason, he was on his back and was forced to get back up.
With that said I don't know that it really matters because he DID pop right back up, easily.
Although Aldo does have good takedowns he is not a wrestler and his main strength is obviously his striking.
Aldo is a totally different beast than McGregor has faced so far. It's hard to say who really has an edge in striking until we watch them fight, in my opinion.
Aldo SHOULD have the grappling advantage though, he should have better takedowns and better BJJ, but again it's hard to say if this will matter. If Conor is able to stuff Aldo's takedowns, or if Aldo will even attempt to take Conor down, if there are no takedowns who wins the striking?
Many questions but they are hard to answer until we watch them fight. The fight could go a number of ways, it really is hard to pick.
McGregor is a beast and his striking is VERY good. Maybe premature to say Conor's striking is as good as Aldo's, but I mean he's proven it in 5 different fights now so again it's hard to say.
Honestly if I had to pick a winner for Aldo vs McGregor, I'd have to go with Aldo via decision, but I can see it going any number of ways really. Should be a good fight.