Yes it is. Even if Bray, Hunter, and CP all leave for the NFL, the foundation for a good running game will still be there. The OL should be good still, the RB's are getting better still by the second, and there is a very athletic group of young WR's on this team.
The front 7 will 3 or 4 NFL players. McNeil will be a year older and Randolph should be back. The foundation will be there unlike when Dooley took over.
If Gruden doesn't work out, the most important thing is to hire a good football coach. I understand the importance of recruiting, but being able to develop players is most important. I think a good coach could win 8 games next year with this bunch.
I know many will disagree, but it's why I'd hire Cutcliffe if it's not Gruden. If Cut brings back Chavis, the discipline and x's and o's will be there. Retain Graham, bring in Martin and another TN guy or two and you've got guys that can recruit to TN as well as coach. To me, that's less of a risk than taking a gamble on an unknown.