I used my upgrade last June when EVO came out, and I will become a silver premier effective 4/1, which is not eligible for a new line discount upgrade after 12-month service anymore (only premier gold can upgrade at a discounted price).
Just spoke with a Sprint rep, he said that I can change my plan to $89.99 before 6/1, which is my 12-month upgrade eligibility point, then I will become a gold premier automatically and get a discounted upgrade. Changing plan will not reset the 2-year agreement, so I can upgrade my EVO on 6/1 after changing the plan in May. Of course if EVO 3D comes out before 6/1, I'll be sad...
Edit: Correction - it looks like I need to stay with $89.99+ plan with at least 3 months, which means I need to change my plan now...