I assume those most all SSD's from major brands (Intel, OCZ, Crucial, Kingston, etc) will eventually support TRIM, right?
Drives with future controllers, yes.
Current drives, AFAIK only Indilinx based and Intel's 'G2' drives will or do support trim.
It is not so much the brand of the drive, more who makes the controller and firmware that dictates trim support.
If you are looking at buying now, Indilinx based drives (Patriot Torqx, OCZ Vertex, OCZ Summit, SuperTalent SuperDrive ME, etc.) already have trim support with the Latest Firmware
Intel's second generation SSD's are supposed to get support in the future.
Current Samsung and JMicrostutter controllers do not support trim and, as I have heard nothing about support coming, I would not expect them to.