If those developers all of a sudden decided to not bother making a Mac version, forcing me to run them under emulation, I might well contemplate a platform switch. But that won't happen unless Apple's fortunes really sink. Photoshop wouldn't be the standard in image editing if Adobe hadn't released a Windows version. Look at how Corel's been struggling desperately to get Mac users to try their Mac version of Corel. Small PC-only programs wouldn't make me switch platforms, but they might make my life inconvenient, or cause me to purchase a PC as adjunct to my Mac.
Software emulation is less hassle and much cleaner.
Mac development have been around for a long time. That is until gamers discovered the emulated performance of games was so subpar few games were even playable, and then only with a high-end Mac. Since then, PC game developers have been flocking to the Mac. Apple needs high sales to generate fresh demand for third-party products. Even if Apple incorporates PC emulation within the Mac OS and new processors push the performance to acceptable levels, only a minority of Mac users would ever purchase PC software.