Yes, there is a VK Leslie sim MFX.
Basically, just like a plethora of different Roland products used to be based on the Sound Canvas and its' derivatives, there are currently a whole bunch of products all based around the Sonic Cell and its' architecture.
The thing is, the GW-8L (and the other world variants) add DOUBLE the sample ROM, so, compared to a Sonic Cell (which has two SRX slots, though), it seems like quite a bargain... You lose the detail Patch editing, but gain double the sample ROM. In particular, the GW-8L has some VERY good Latin percussion added to the basic ROM, and this tips the scales in favor of this, for me, because Roland do NOT make an SRX card to add these back in to other Sonic Cell derived keyboards. If the Sonic Cell had these kits in it, I'd probably already have one, but noooo...
My friend who I borrowed it from back in Winter '08 put it back in the store on consignment/layaway (couldn't get on with no style editing), where it has languished until now. Today, we went and got it back, and I'll probably do another review after we upgrade it.
Stay tuned.