Tricky choice, but there's a couple of things to consider. You said you plan on upgrading to a more expensive house, so you might save more on the new house post-bubble than you'd lose on your current house. Suppose you want to move from a $1M house to a $1.5M house - you'll need $0.5M. The bubble bursts, and housing prices fall 20% across the board. Now you have an $0.8M house and want to buy a $1.2M house, so you only need $0.4M to make up the difference. That's a big assumption that housing prices fall equally in all areas, but you get the idea.
The other things to consider is how easy it will be to sell your current house. Housing prices fall because the demand isn't there. Even with a lower price, you may have more trouble finding a buyer post-bubble, so consider how important timing is for the sale of your current home.