Only DTs in the Draft I can see being taken ahead of RJ McIntosh:
Christian Wilkins (6'4" 300lbs)
Vita Vea (6'5" 340lbs)
Da'Ron Payne (6'2" 309lbs)
Dre'Mont Jones (6'3" 295lbs)
Derrick Nnandi (6'1" 313lbs)
Trenton Thompson (6'4" 295lbs)
Taven Bryan (6'4" 291lbs)
Harrison Philips (6'4" 285lbs)
Rasheem Green (6'4" 276lbs)
RJ McIntosh (6'4" 291lbs)
Kendrick Norton (6'3" 312lbs)
So in the worst case scenario if McIntosh declared early, he'd go top 10 DTs. There were 12 DTs drafted in the Top 4 rounds last year. And Another 10 drafted in rounds 5-7. Having said that I think Kendrick Norton would be making a big mistake by leaving early. Rj McIntosh is having a great year though, so I think he would be picked in the first 2 days (=1st, 2nd, or 3rd) of the draft for sure.