Wilfork should definitely be in, as one of the best players of all time at his position - which is an impact position. But I expect it will be a struggle for him, because it's not easily measurable. It's not a position that racks up stats, and in the common fan's mind isn't easily distinguished from other DL roles which do rack up stats. It's like trying to get a dominant interior OL or RT into the HOF - an uphill battle. Out of all of them, I'd say Wilfork changed any given game the most. He forced offenses to pay special attention to him and adjust what they could do, and broadened the range of what defenses could do because of his dominance and flexibility. He made the DL on either side of him (including Seymour, IMO) better, and the LBs behind him much better.
Rodney should be in over Polamalu and Lynch; I'd put him about on par with Dawkins when considering their level of play over their entire career, though I'd say Rodney had two peaks - the first was the more typical peak where the end of his physical peak coincided with the development of his high football IQ and experience. The second was at the tail end of his career in New England, where while his physical skills had started to decline, his football IQ and overall impact exploded because of the education under Belichick and the perfect way he was deployed to suit his skills and abilities.
I like Seymour, though I've always thought that Patriots fans probably overrated him a touch. He was definitely one of the best DTs of his era; not sure how he stacks up vs. those who are already in or under consideration. Personally I have very high standards for the HOF, less about longevity than about dominance. Was there any year where we could say that Seymour was the best DT or (3-4) DE in the NFL? Maybe. I don't think so. If you take away the impact of Wilfork playing next to him, did he regularly force offenses - particularly those that had a high quality OL opposite him - to adjust because of him? I could be wrong, but I don't think so. The biggest problem for opposing offenses was that they so often already had a 2nd OLman helping with Wilfork that they had to rely on other means of helping with Seymour, which put them in a bind.
McGinest would be borderline except that he was so clutch when it counted, that probably pushes him over the edge.
I don't think anyone else is clearly in.