There is an exploit even in future firmwares. Thanks to Nintendo deciding to use the Tegra!!
But yeah, talking about the usual normal exploits, that too, just not now.
Easy: Gbatemp will announce it if it is release already. Did they released it already ? Hmm.. nope. Not yet. Keep your eyes on GBATEMP front page everyday. Thats all.
There aren't any publicly accessible ways to access homebrew right now unfortunately. At least when you do get homebrew there will be more apps for it so i'd suggest waiting for it to come to 4.x.x