Yep, but your going the wrong way! Usually people go from the 1 slot to 4 or 6. Anyway if you have a 4 slot and go to a one it will work but your Game Select button will stand out like a swore thumb. Going the other way say 1 to 4 you need to install a button (Real easy) and connect it to Pin 26 on your harness.
Yes It will work fine.....But think about what you want. A 2 slot may run you $500 and a 4 slot $600. You will want the 4 slot, trust me. I am considering running duel 4 slots with a Board Select button. This stuff can get expensive so get what you want up front.