Well, if they believe that, then they're almost certainly right there, too.

  * New construction isn't going up fast enough, so the housing supply will decrease and 
  * the number of people that want to buy a home increases as long as the total population of an area increase. Bundle that with
  * fewer people getting married, and you need more houses per person than before, and that further reduces the housing supply; AND, further that with the reality that
  * houses are seen as an investment vehicle, so anything that reduces the value of a house rather than increases it causes people to recoil back because that's literally their retirement in there (see Australia's housing situation, for example)

Housing prices can only go up without the entire financial system changing.

It's a very, very good bet as long as major things don't change.