With three starting caliber TEs, it wouldn't surprise me to see Hernandez line up as a WR - that would allow them to have Hernandez, Gronk, and Ballard - not to mention other running/pass catching options like Woodhead - all on the field at once providing a pretty good offense even if Welker doesn't return.
Those are all great short to mid field options.
What the team lacks is someone to stretch the field - and despite all the catches those guys bring in, don't think for a second that Belichick doesn't realize how much a difference that can make in opening up the field for everyone on the team - not to mention reducing the pressure and the hits on Brady.
In terms of the draft, a deep WR is a position that typically requires some development. It's an area where the differnce in the speed and duration of the college game, compared to the pro game, really shows up in a big way.
So if the Patriots draft a WR, don't be expecting instant production. It can happen - but usually, if they're lucky, a player will develop in 2-3 years.
If you want someone NOW - and I think Brady and Belichick are getting a little impatient for Super Bowl #1 - that probably means you're going to have to pay a little bit for a proven deep threat.
But IMO it's worth it.