I don't think its a bad thing to have other musicians joining the band. I think collaborations with other artists can enhance creativity with awesomeresults and those artists deserve credit for their work, if they aren't just producing.
But that said...I'd like to see something new. There was some discussion about this in another thread on the sub side and I in agreement with the sentimentthat it's time for U2 to get out of its comfort zone, to get pushed around a bit and for something really new. Time to say buh-bye to Eno and Lanois.