Well it's a definite possibility as Hotel Richissime is located in Lumious City, the same location as Lysandre Cafe and Lysandre Labs. Malva who is a member of the Elite 4 and ex-member of Team Flare can also be fought in the hotel as part of one of the missions during the Looker sidequest after upgrading the Mega Ring.
So I'd say it'd definitely possibly but as of right it's unconfirmed, maybe when Team Flare or Hotel Richissime appear in the Anime it will bring us more hints as to whether or not Hotel Richissime is related to Team Flare, but as of right now we can't say for sure.
On a separate note:
>A man at the reception desk will let the player stay overnight, healing their Pokémon, at the cost of 100,000 Pokémon Dollars.
If that's not robbery I don't know what is! xD