Tobey is over 40 years old now. And I highly doubt he'd want to be in the MCU. Neither would Sam Raimi for that matter. Not to mention even if Marvel gets back the rights to Spider-Man Sony will still own the Raimi films and therefore Disney won't be able to use them. I suppose if Sony had just made the deal with Disney then it could've happened but I doubt Raimi, Tobey, and Kirsten would be on board with joining the MCU. Raimi is an independent film maker and I doubt he'd be on board with having to include certain events from other MCU movies in his movies he works on in the MCU. Plus he hated being forced into using Venom and it's not like Marvel Studios wouldn't make him use certain characters anyway. He was probably through with big companies like Sony after the Fiasco of Spider-Man 3 and that's why Spider-Man 4 never got made. There was a rumor Carnage would be in Spider-Man 4 and it could be Sony was trying to convince him to use that villain that made him quit.