It may sound far-fetched but it's certainly possible. After all, no R1b has been found in Europe before a Bell Beaker site from the 3rd millennium BC and today many Europeans (most in western Europe) belong to this haplogroup. As more Y chromosomes are sampled from ancient Europe, it will become clear if the R1b frequency actually shot from non-existence to ubiquity over a short span of time, and the Y chromosomes after the transition will be practically clones of each other.
Investigative Genetics 2013, 4:25 doi:10.1186/2041-2223-4-25
Modeling the contrasting Neolithic male lineage expansions in Europe and Africa
Michael J Sikora et al.
Patterns of genetic variation in a population carry information about the prehistory of the population, and for the human Y chromosome an especially informative phylogenetic tree has previously been constructed from fully-sequenced chromosomes. This revealed contrasting bifurcating and starlike phylogenies for the major lineages associated with the Neolithic expansions in sub-Saharan Africa and Western Europe, respectively.
We used coalescent simulations to investigate the range of demographic models most likely to produce the phylogenetic structures observed in Africa and Europe, assessing the starting and ending genetic effective population sizes, duration of the expansion, and time when expansion ended. The best-fitting models in Africa and Europe are very different. In Africa, the expansion took about 12 thousand years, ending very recently; it started from approximately 40 men and numbers expanded approximately 50-fold. In Europe, the expansion was much more rapid, taking only a few generations and occurring as soon as the major R1b lineage entered Europe; it started from just one to three men, whose numbers expanded more than a thousandfold.
Although highly simplified, the demographic model we have used captures key elements of the differences between the male Neolithic expansions in Africa and Europe, and is consistent with archaeological findings.