I wouldn't think so. Paola's doubles have not hurt her singles at all, I think in fact playing doubles has helped her and kept her going when the singles results were a bit disappointing. The fact that they are at different places in their singles career is not a bad thing at all, it means Vivi can concentrate more on the doubles. Most sucessful doubles teams are made up of people who are not competing against each other on the singles.
It is one thing to want to "concentrate" on doubles, it is another thing to kick a golden mine goodbye, Paola and Vivi have been making millions together and winning GS titles left and right these last four years, I am sure for as long as the results keep up the partnership will continue (unless they had personal differences, but that seems unlikely).