You won't lose any points already in your WyndhamRewards account.

The only points you would lose is if you did spend "too soon" before cancelling the card and those points from that spend hadn't posted yet at the time you cancel the card. Or if there was some bonus you had earned on the card that hadn't posted yet at the time you cancel the card.

So any points that still have not posted to WyndhamRewards you lose, any points that have already posted to WyndhamRewards you don't lose.

And that's the way it works with every airline and hotel card I've ever heard of, at least if you only do it once. Some programs may wipe your whole points/miles account out if you try to apply and cancel and apply and cancel and apply and cancel and apply and cancel for the program's credit card over and over and over and over again and yet earn that program's points/miles no other way. I've not yet heard of a hotel doing that; Alaska Airlines does appear to have done it some cases of extreme "abusers" (from the company's viewpoint):