Brainpool has released a statement on their homepage saying that their bassist Christoffer Lundquist is indeed on Roxette's forthcoming album. He will play the bass and sing backing vocales. However, he's not a member of Roxette band and he won't be one.
The news page also tells that Brainpool has spent the Autumn writing songs, recording demos and auditioning for a new singer. The Brainpool Homepage / News