I would hate to sell a gun, any gun but it is all up to what YOU want. I use one of my G30's as my everyday carry and I think it is the Best Glock ever made. If you think you can purchase one in the near future without selling then I wouldn't sell but if the prospects are slim that say with in a year you will be able to buy the 21 or 30 then I would say make the best deal you can and get the Gun/Caliber you want. Tomorrow is not promised to us so If you want it and the only way to get it in the foreseeable future is to sell/trade the 23 then as Nike would say Just Do It! We do not know your finances so only you can answer that question! BTW I would get the 30 if it were me. I have at least couple of each (21/30) and the 30 to me is the absolute best! 21's are good and I shoot mine but the 30 for me is more accurate and easier to carry!