If they do plan for another bear species, I hope for Brown Bears (Swiss icon) or Polar Bears, currently there are no Polar Bears in any of Switzerland's several excellent zoos.
There were kept both these species, I think 10-15 years ago, exhibited the Brown Bears would be a better option, Basel is a small town zoo, they have not enough space to create an exhibit for Polar Bears regarding at currently husbandry guidelines. Mayby they will keep Malayan Bears, there is only an elderly female left in the zoo so they might restart with keeping this species till the new exhibits for Apes are finished.
I saw Brown, Spectacled and Malayan Sun Bears in Basel when I visited for the first time in 1999 but the Brown Bears were gone when I visited next in 2006. I think they stopped keeping Polar Bears only one year or two before I visited in 1999; I think I saw Otters in the old Polar Bear exhibit.
My guess would be they will continue keeping Spectacled, or Sun Bears- both smaller species that an urban zoo can house okay. I think it will only be one species though. (either or...)