Actually Funimation announced that for Season 1 of Railgun they will re-release it on Blu-Ray I can't remember if they had a set date.
Which sucks because Season 2 just came out on DVD only on will take forever for a Blu-Ray release. I actually waited on Season 1 and passed on the DVD only release so at least I don't have to re-buy it.
Index I got burned on Season 1 and might re-buy the whole franchise down the road but they just took too dam long to release it over here for some reason.
As for why no Blu-Rays even after 15 months is because Kadokawa sucks and won't let a Blu-Ray release for a long time until after the Japanese release had been out. And of course Funimation keeps it's mouth shut whether they even have the Blu-Rays rights for those who are willing to wait.
I really like the Index and Railgun series and I'm really glad I said screw the dvds. Bluray or nothing is my motto.