I can't see this happening for two reasons;
1. Pally heals are designed to be weaker but more mana efficient than other classes, a flat increase on every heal (500 on holy light!) would bring us closer to priests on raw healing power, both upsetting the balance and losing the individuality of pallys.
2. It makes a 4th or 5th pally in the raid redundant in buff terms, at the moment 4 pallys is the upper limit for a 25 man as every class would get kings, wis/might, salv and light. If every pally had light then this "soft cap" would be 3, any more and a resto druid or holy priest would be preferable. We typically run 2 or 3 pallys on a 25 man raid, but this would be restrictive for guilds who run more.
It also wouldn't free up the use of other buffs much. Light is the lowest priority buff on most raid members, with the exception of tanks. On a 25 man its usually only used if we have 3 pallys, as the extra threat from might is generally preferable to a bit of extra healing from two of the seven or even eight healers in the raid.
Edited, Apr 15th 2008 7:40pm by Tinyknight