However, this sign on I-80 implies that the route between Vegas and Reno is via Yerington, not Fallon.
The Yerington route is also plausible, but the Fallon route is used much more often (it's generally the first option that comes up in driving directions on mapping sites). The Alt route via Yerington is 3 miles longer, and has longer stretches of slightly lower speed limits. Taking Alt 50 and US 50 to Fallon is now completely 4-lane, which is a plus (when you just want to get through the drive).
I think Vegas is mentioned on this sign because the next supplemental sign directs long-distance travelers east (toward Fallon and Ely) as opposed to south (Yerington, Las Vegas). I actually wish NDOT would put up a sign that directs to Vegas via either route.
I wonder if the I-11 freeway gets built, would it bypass Reno, or go into it.
Also since current traffic volumes don't seem to justify I-11, is it a "If they build it they will come" type of plan?
The I-11 study proposals look at extending north from Vegas in a multitude of directions towards Canada. A lot of speculation is that it would connect to I-580 in Carson City and Reno, but that is not a given. The goal would be what route efficiently moves trucks and goods, and a direct link to Reno may not be best considering how you'd tie that in to points further north. An earlier idea reported in media had it following much of the US 95 corridor north, and the US 93 general corridor through eastern Nevada would also be a viable option--it all will depend on where the demand will be.
I doubt this will lead to a major "if they build it, they will come" scenario. Look at I-80 through northern Nevada. No new towns have sprung up along that highway since it was constructed through the 60s-80s. Except for maybe Elko, no town served by I-80 has had significant growth due to the I-80. Central Nevada is sparsely populated as it is (much less populous than the region served by I-80), so it is very doubtful that a new north-south interstate will spur significant growth.