The XL3600 is not based on PageWide tech but traditional inkjet with the moving printhead. The idea was to build it in the look of PageWide XL (and competing laser/led devices) with the trays for the paper rolls so it looks more robust/reliable to the end users, but the device itself is essentially a redesigned version of the DesignJet T3500.
This is targeted at the entry level market to compete against mono laser such as the MP W6700. The selling points are that you can get a colour device for similar starting price as the W6700 and close enough mono click cost (so you don't need two devices as you mention).
Print speed wise it's half the speed as you say, but it's faster to print the first 5 pages (as it doesn't have the fuser to warm up) which covers most of the print jobs in the target market.
I would agree that your monochrome fleet is in danger when these start to become widespread. The XL3600 only came out 6 months ago but I've already switched a few Ricoh customers with this model.
