as for the GBA getting a clock speed increase i don't think that will happen. even if nintendo purchased arm7's in bulk that were capable at running at a faster speed to get a bulk discount, i'm pretty sure they would clock them at stock gba speeds. the last thing nintendo needs right now is to devide it's GBA user base any more than they already have with the DS.
As I said the clock boost is only for multimedia ie decoding MPEG at 30fps. At 16MHz, the ARM7 is not capable of decoding video at 30fps. The clock boost can be programmable and not locked at 33MHz no different from the 33MHz ARM7 in DS.
This new GBA SP will serve the same purpose as the PSTwo ie increase sales.