Its not wrong to think that about their relationship and in a lot of ways the sooner its over the better, however depending what place you wife is in, if its over too soon she might not be ready to give you another chance and so would look for someone else.
Its not a pleasant thing to do but think long term and ask yourself what is the SECOND best outcome from all of your situation. See what you feel toward the BF then.
I'm confident everything is fixable if you're both willing
Both mid 30s, 2 young kids BD 7sep14 XW moved on long ago, now living with OM1 D paperwork in progress