No. The Sentry is great for the books, but to actually include him in the team would require an enemy way beyond the Avenger's level to appear. I feel The Avengers should deal with something on a global or galactic scale, not a universal one. The Collective equalled out with The Sentry, and it made every other Avenger outside of The Sentry bush-league. I'd love to eventually see a standalone movie or series with The Sentry, but putting him in The Avengers brings with it all the problems DC and Superman entail what with the presence of people who can blow the universe into dust particles would be haphazardous and hard to bring to the big screen with today's tech.