So... it looks to me like EL wire requires an inverter to supply a high-frequency (and relatively high voltage at around 90v) current to it to glow. A small inverter capable of driving 1-8 feet of wire draws about 200ma @ three volts. In theory then, yes, I suppose you could drive that off the TERMPOWER line on a SCSI chain, as TERMPOWER is per standard supposed to be able to supply about one amp at five volts. (Although there are different figures for this; one source said 900ma, another said up to 2A, and there are also considerations related to voltage drop over long cable runs.)

Practically speaking, though, it sounds like a sort of crummy idea. It would probably be safer to tap your 5v more directly off, say, a SCSI enclosure's power supply and drive your blinkenlights indepenantly. A typical LED like you might find in a light-up external terminator only pulls about 20ma; that's a tenth of what an EL cable run will draw and I'd also worry a little about a cheap little inverter putting noise on the data lines if you pull from TERMPOWER.