This indicates to me that these foreign buyers are not necessarily institutional investors or companies, but foreign citizens, so the segment of the market they're in is probably not the multi-million property segment, but the more "standard" residential properties market a normal US resident would be in. The article does somewhat confirm this:
>"Foreign buyers include those living in the U.S. and overseas, but the majority (60%) were recent immigrants and foreigners who live in the U.S. for work, school or other reasons."
If you also take into account that there is an effect of the purchases made by these buyers on the "median price for all buyers" cited above (and so the real difference in median prices between foreign/domestic buyers is higher than what is suggested by those figures), I think the effect is somewhat diminished (as this pushes them into a more "upscale" market).
Even with the above, I still think it's relatively safe to assume this will have a downwards impact on US residential prices, at least in these states (but I'd need precise figures as to what share of homebuyers are foreign).
*edited the last paragraphs to correct something I had gotten mixed-up on