I compiled a list of SGs (or players who see a fair amount of time at the 2) taken in the 1st round from drafts 2006-2015 with wingspans no longer than 6'8. The further back I went, the harder it was to find wingspans listed, so the list isn't 100% accurate (I didn't list them if their wingspan wasn't available).
Make of it what you will:
JJ Redick - 6'3
Steph Curry - 6'4
Jimmer Fredette - 6'5
CJ McCollum - 6'6
OJ Mayo - 6'6
Rudy Fernandez - 6'6
Randy Foye - 6'6
Terrence Ross - 6'7
Tim Hardawy Jr - 6'7
Austin Rivers - 6'7
Dion Waiters - 6'7
Rodney Stuckey - 6'7
Garry Harris - 6'7
Jrue Holiday - 6'7
Brandon Knight - 6'7
Avery Bradley - 6'7
Brandon Roy - 6'8
Devin Booker - 6'8
Nik Stauskas - 6'8
Zach LaVine - 6'8
Kentavious Caldwell-Pope - 6'8
Brad Beal - 6'8
Evan Fournier - 6'8
Evan Turner - 6'8
Gordon Hayward - 6'8
Rodney Hood - 6'8
Eric Bledsoe - 6'8
Russell Westbrook - 6'8
Daequan Cook - 6'8
Maurice Ager - 6'8
*Interestingly enough, the two tallest players from this list are Hood and Hayward.
You could add Wes Matthews to that list too. He measured at 6'8.25, so basically 6'8.
*NVM, didnt read 1st round*