You can breed any two guppies you like. The outcome will be uncertain as to what the fry look like.
Also the female retains the male's sperm for quite awhile so they will probably drop maybe 6 more batches of fry before they have some from the new male. It may not happen like that but if you don't replace the male right away you'll still have guaranteed fry from at least one of those females again.
Brenna