If your neighbour is happy to do this, it's probably a good thing if he's more a territorial cat than a family cat anyway - but I have known of people saying this before just to put people's minds at rest and then thinking 'sod it, it's only a cat, it can fend for itself.' It's true that cats can, if they must (and will even if they don't have to, as sport/play), but to make them depend on that when they've never had to know it is a completely different matter.
You should ask your neighbour to be honest with you, then you can make a proper decision about what to do yourself. The trouble is, if you move, you will probably have to keep him in for some time anyway; otherwise he'll just run off trying to find his old stomping ground. If you can put up with the keeping him inside with a litter tray for a month or so to begin with, until he sees the new house as home, then you'll be OK. If you can't, perhaps you shoudl try to rehome him - but to someone either close by so that he has the same territory, or to someone who will do the right things to stop him running off and trying to find his home.
I know it sounds a bit OTT, but cats don't think like us. Whatever happens though, you've been there for almost 12 years of his life and if you suddenly disappear, that will be almost as traumatic for him as losing his territory.
I hope everyting works out for you and for Tom too.