Markus, I am still rather new to this, but am Marriott Plat, and wish I had gone Hitlon (am gold) or Starwood(gold there too), so I am not going to address your question about upgrade (don't know).

As for promotions the following shows when you sign into your account on-line -- just click it (after signing in) and you will be registered.
"Sweeten your summer with the Marriott Rewards 25K Bonus!
From June 15 through September 15, 2001, you'll earn 5,000 bonus points with every third stay at any of the more than 2,000 participating hotels worldwide - up to 25,000 bonus points."