This e-mail went out to affiliates:

Starting April 1st 2017 we will be focusing on our ongoing Free Welcome Bonus Offer. In addition, our branding team has designed some wonderful creative and banners to help support your acquisition efforts and drive in some big numbers!

Therefore, as of midnight March 31st 2017, all Cristiano Ronaldo & Neymar Jr promotions materials (ie. banners, images, etc) will have to be replaced as the Cristiano Ronaldo & Neymar Jr banner creative will no longer be valid for you to use from that date.
Amaya already fired a number of poker pros since they bought the company from the Scheinbergs, but they've been pretty aggressive with signing actual celebrities such as Ronaldo and Neymar Jr.

Now it seems they're done with that, too.

Here's a pretty good writeup on the situation:

Oddly, Amaya has not announced a new marketing strategy to replace the Ronaldo/Neymar one, so they might just be cutting costs and deciding to just go with traditional advertising.

I have mixed feelings regarding this decision. While I agreed that most of the poker pros were a waste of marketing $, major stars such as Ronaldo and Neymar Jr do have an astounding reach, including on social media. I could see the value in having them, but at some point the cost is probably too much to justify.

Perhaps Amaya realizes that Pokerstars has enough brand recognition at this point to where people know how to find them, and they don't need to spend as much on advertising.