Manor proper (the John Booth/Graham Lowdon version) is still in the process of getting its LMP1 team going; I really can't see them contemplating any other series, let alone F1, in the near future. When Liberty first bought F1, Manor said they would consider re-entry, but then they got a deal they couldn't refuse for LMP1 in WEC, so they're making the best of that right now.
John Booth combines the WEC work with assisting Toro Rosso, so it's not as if he isn't staying involved in F1, but I think that given their previous experience, they'll be wary of any questionable promises made from F1 in future, and any attempt at re-entry will be several years in the future, if ever.
I could see a dreamer such as Steven Fitzpatrick (the last boss of Manor F1) retrying with a new team or a buy-out. If the latter is attempted, the wise boss will run 100 miles in the opposite direction, as he has been shown to back out of deals mid-stream (he was meant to be at Manor long enough for 5-year repayment schedules to be met, even though those schedules were why he was allowed to buy its debts for 2.49% of their value in the first place...) I would suggest that if any Manor activity is happening in F1 (and I've missed the rumours entirely), it would be from that quarter.
I am a Manor fan. They are not only great, solid racers, but they also have a sense of humour (they giggled quite a bit when I brought them manor cake last year) and really enjoy interacting with their fans (they always say "Hi" if you speak to them and they always read messages sent to them, which even in WEC, is apparently beyond the ability of some of their fellow teams).