46 olineman total(modern era), so it is hard to get in as a lineman and doubly hard as a pure guard - 40% of the online positions but less then 20% of the lineman in the hall are guards. The last pure guard to get in retired in 1993 (Mike Munchak) and only guy since him was Larry Allen who played tackle for a large part of his career.
So unless they move outside, it's unlikely either, let alone both, Nelson or Martin get in.