Other than the free upgrade from win7/8.1 (which is nothing to do with PCS specifically) I don't think there will be any - PCS tend not to do special offers in general, they just offer the most competitive prices they can.
I don't think the release of windows 10 will bare much of an impact on the sales of PCs personally - MS are offering a free upgrade to Win10 with any Win7/8.1 purchase so there is no upside to waiting I wouldn't say.