Without any source, game journalist and insider Marcus Sellars has posted a message on Discord stating that Vanquish 2 is in development, and that it may well be an Xbox One title. The first one was developed by Platinum Games with Shinji Mikami as the producer, but Sega owns the rights, with Mikami since leaving the company to run his own studio Tango Gameworks (makers of The Evil Within).
We really have no clue how Sellars has got this information and how reliable it is, but it's been reported that Microsoft is investing a lot in more third-party titles, not to mention the fact that Vanquish has just recently become backwards compatible. Like we say though, there's very little detail or information on sources, so take it with a heap of salt.
Would you want a Vanquish sequel?