I don't think Mugen will offer a conversion kit, but you can order the parts to build one now. Basically it's the current MBX5 ProSpec but has the following parts off the X5T truck:
Front & Rear Shocks/Springs
Servo Saver Spring
2.4mm and 2.9mm sway bars
Then a new set of taller buggy shock towers to accomodate the longer shocks. If you own a MBX5, I'd get the shocks, towers, springs and new servo saver and update your current ride (I already ordered the parts
The current front lower arms are revision 4. They are making a new set of lower arms for the front as the Rev 4's are breaking at the pillowball. They may offer a new set of lower rear arms too. I noticed the truck arms have 3 mounting locations instead of two. I'll run my current buggy and use up what arms I have now and then order new arms later on down the road.