Reinforcing Mr. Green's point - it may be an area-specific concern (I'm in Quebec, Canada), but the price of building materials went up quite a bit in the last year (double for lumber, scarcity in items coming in from abroad, etc.) so you'll have to consider if you would really be "saving" money if you decide to build in the next couple of months.
+ all other concerns mentioned above.
If I did not own 2 properties right now, I would definitely be renting for a little while to see where these crazy times (potential markets and housing bubbles) will lead us...
It's a weird time right now.
^^^