Not worried about Gronk. They literally have been playing OT's at TE this pre-season. They had 0 healthy TEs, and even when healthy, they only had one pass catching TE. Hoo-man is an extra OL and can't catch anything. This should allow Pats to continue using 2 TE sets.
Mankins is 32, is a run blocking beast, but struggled in pass protection last year. I think I heard he allowed 12 or 13 sacks last year, which is a lot for a Guard.
This is BB selling high on a guy he probably views as being on the downside, if even just slightly. Cleared a lot of cap space to perhaps extend guys like McCourty, Gostkowski, Connoly, Solder, Slater, and Vereen, all could be FA at end of the year. Not to mention Revis.