Do you think it will be possible to retrofit a current P365 once they release the manual safety version?

Since SIG hasn't actually produced one yet, that anyone has actually used, it's very hard to say.

Considering that a manual (specifically, thumb) safety was developed as an after market item for Glocks, of all things, if Sig doesn't mske them available as a retrofit, someome might well be clever (or brazen) enough to exploit that opening in the market and create a retrofit. I
might even be interested.

Personally, I liked the grip safety on the ill-fated Colt Pocket Nine I owned; it brought me some added comfort in the appendix carry. It served a purpose, but didn't require learning to sweep a thumb safety off (or on), which may be why John Browning liked 'em. It would be too wonderful to think we'd ever see one here; it'd have a hushpuppy's chance in Antartica (too many snowballs in hell; it is getting cold down there).

I REALLY miss that pistol. Mine was superbly accurate out to 25 yards, with great sights and trigger, and 100% reliable. I wasn't an idiot the day before or after I sold it, but I sure was on the day inbetween!