If they haven't by now, they probably are holding until block 210,000. There's little risk to just seeing what happens.
That would definitely make mining more profitable. I'm not convinced though. It isn't a shock that it will occur -- and a lot of speculative buying has already occurred with the expectation of a rise. If it doesn't happen, there could be a lot of dumping instead.
There's still a month backlog of FPGA shipments even. Plus, even if the ASICs aren't shipping, doesn't mean they aren't mining!
Nobody knows for sure, but I would bet that unless the exchange rate rises, mining profitability will be decreasing from here through block 210,00.