BitShares is simple, unified, and captures what it is without extra overhead or the need to explain more. It is easy to say, spell, and use. It parallels Bitcoin nicely.
X sounds eXtreme or "over hyped" or "advanced" or some other feeling that people don't get or like.
My feeling is that
some people would see the "X" as a bit naff, aimed at youngsters, and with potential to become dated quickly. I'm thinking along the lines of products from the 1990's being described as "mega" or "super".
A change of name would also make it clearer to people on the fringes that the proposed alterations to the ecosystem have occurred.
Imagine if the name remained the same - when additional shares suddenly appear on coinmarketcap, potential investors who aren't completely in the know could think,"WTF, what are they playing at, suddenly increasing the supply to cheat?".
However, if the name changes at the same time as the available supply going up, people watching coinmarketcap could think, "Oh, BitShares has changed - I'll have to look into that".
Know what I mean?