1. Spike King's reply to that November Hightower tweet says that Cannon would also be retiring, which appears to be entirely debunked. He also has some history of other big misses, recently predicting week 10 Pats/Falcons in London, week 11 bye, and week 12 Pats/Bucs on Thanksgiving. Yikes.
2. Of course it's not guaranteed that Hightower will be back. If he doesn't have a strong offseason and training camp, then they're not paying him $10 million next season. It's a positive that his physical after the season went well enough that they didn't cut him on the spot, but that evaluation will be ongoing, perhaps as soon as next week's OTAs. If he doesn't feel like he can live up to that contract, then it could also make sense to go out on his own terms rather than going through a whole training camp only to get cut.
3. It appears that Chung's retirement will be official after June 1 for the cap benefits. There's no benefit to waiting with Hightower since he's in the last year of his contract. If they had an answer on him, then they would have made a move earlier when there were more ways to spend that cap money.
4. The first tweet is from patriotnews247, an imposter of patriotsnews247, who is a real person attempting to break Patriots news. The real account has reliability issues of his own, which the imposter account appears to be poking fun at. There's some real drama right now about whether the imposter is Spike King himself, somebody from his "Pats Chat" group, or an entirely separate third party.