It works this way... so long as you get a relatively high-end card (as the 560 is), any games that don't support SLI are old enough that a single card can run them just fine.
I can't think of any modern, or anything in the last 5 years, game that does NOT support SLI. That said, consider the trade-offs. The 570 is an outstanding card, and until you get that 'eventual' 560 (which you may never end up getting for whatever reasons), the 570 is the better performer. At 1080p, a faster single card is preferred by most people over dealing with multi-GPU setups -- the main issue is not whether SLI/CF is supported, but the issues that arise because of it (microstuttering, rendering errors, more heat produced and power consumed, louder, etc. etc.)