Spiderman in the MCU
Let me start by saying, if they pulled it off, holy cow, that would be amazing, like holy cow, blow up the world, amazing. It would never happen however. The primary reason being, Sony has rights to him, and seeing as it is their big cash cow, I can't see him going cheap enough to make any kind of real intrigue for Marvel. The second reason is less business, and more fan interest. Marvel has proven they want to make awesome movies, who doesn't. But what sets them apart is that they are good at it. I am no director, but I have a hard time finding a way to introduce him into the series without giving him a solo movie and then being recruited, like a lot of phase I characters. The final reason he would never make it in is back to business reasons. With this generation of superheo movie watchers already knowing the styling and actors of this generation's spidermans, adding him to the MCU just seems unnatural without getting the actors at least, and probably even a bit of the styling element of the spider films into at bare minimum his intro film. The final reason- Sony isn't done with him. He has his own gig rolling with Sony, and they aren't likely to disrupt that by letting him in other movies or the actors spend time on another set.
Wolverine in the MCU
Pretty much the same story as before. The only change is that the Avengers have a long story with the X-Men. How that would all be sorted out-anyone's guess. I doubt again that they will be able to get him, but it would be fun to explore the possibilities.
If anyone wants me to explore another topic, specifically Marvel, let me know, I have school but will see what I can do.