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Kurzaa
What would be the price difference between two hotends vs a single hotend?
Very little, given that the stepper motor drive is a plug-in board. Dual-extruder printing is becoming very popular these days, so I think it's worth supporting. RAMPS supports dual extruders if you don't also want a controllable fan. E3D are selling two different dual extruder nozzles (Chimera and Cyclops), and it's also quite easy to convert some other hot end designs to dual nozzle (e.g. see my blog entry on converting the Ormerod to dual nozzle).
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Kurzaa
Also, I only skimmed the list, but don't forget pins for fans, servos, and LEDs. Probably my biggest gripe with my current RAMPs board.
The expansion connector would have about 10 uncommitted I/O pins + 5V and 3.3V power for those sorts of thing, although up to 5 of the I/O pins would commonly be used for attaching an LCD control panel and encoder.