Your strategy makes perfect sense to me.
… if it were 1999. But, unfortunately, it is 2010 and I think we are not yet positioned for this strategy to work out. In your shoes, I would wait another 2 years, then reconsider this.
Assuming that your move-up place is in a higher-end area, the dynamics of the market favor waiting. I don’t see significant danger of large up-side moves at the higher end of the market, and we are likely to need to see some equity build up in the starter homes before there is signficant upward pressure on move-up homes.
Of course, my opinion is biased by interpretation of what I would consider move-up areas. What area(s) are you considering for the move-up home ? What area is your present one?