Ups,didn't know ; I thought like that because I didn't see yet plugins process and clever .jar packing resources , which I saw in ff4b with gecko2
Both of those things are independent of having Gecko 2, but the former (plugins in separate processes) is now enabled in SeaMonkey 2.1 nightlies, the latter ("omnijar" packaging) is in our plans for SeaMonkey 2.1 but will probably only happen after 2.1 Beta 1.