Elektron Musical Instruments

I'm just about ready to purchase a MachineDrum but the UW has got my 
attention now after listening to the demos.  My question is this:  
will the upgrade path always be available?  I'm stretching my budget 
to the limits as is and was hoping I could add the UW features in the 
future.  For now I'll be using the MD alongside a Korg ESX.  Maybe 
this combo is enough??
-grimley