I believe there is posibility it is true . For White Croats in Krakow aeria I believe they are Sarmatians . Vandals who use to live in Poland could also be Sarmatians . And there could be even more Sarmatians that settled Poland during they move to west .
There is also legend about Sarmatian origin of Lithuanian nobility , and Lithuania and Poland use to be in same state in Midle Ages . There is 6% of I2a in Lithuania and only 1% in Latvia , and they are neighboring states and they are both Balts . This diference is suprising and could give some weight to claims of Sarmatian origins .