In a lot of the tank/rebuild threads people have been advocating for trading Kyle Lowry, with the usual sentiment being "he isn't a starting point guard." Naturally there are those who disagree with this proposition, and that's fine. This thread isn't to say that Kyle should be traded or not. This thread is, instead, to address what other options reasonably exist at point guard.
PG is a deep position around the league. There are a lot of good point guards in the NBA right now. But how many of those good point guards are obtainable by the Raptors?
Untouchable: Steph Curry, Chris Paul, Mike Conley, Kyrie Irving, Derrick Rose, Ricky Rubio, John Wall, Ty Lawson, Tony Parker, Damian Lillard, Russell Westbrook, George Hill, Deron Williams. These thirteen point guards (and we're already more than a third of the way through the league!) are not going anywhere (except possibly the Lakers, you always have to account for the Lakers). They are locked up on longterm deals or rookie deals that will be extended. They are the top stars of their team or at worst the second-most important stars on their team except for Mike Conley and George Hill (who perfectly complement their contender teams' systems and thus can't be moved easily). We have no equivalent star to trade for them unless you move Jonas, and even then, maybe Jonas doesn't get it done.
Probably too expensive: Jrue Holiday, Kemba Walker, Jeff Teague, Rajon Rondo. These are all damn good point guards and not the cores of their team, but that is not to say these players aren't valued highly by their teams. Would the Pelicans trade Jrue Holiday if the right trade came along? Yes, but Jrue Holiday cost the Pelicans their 2013 first-round pick (Nerlens Noel) and their 2014 first-rounder. That's two first-round draft picks, one of which was in the lottery and the second of which might well also be. That is very, very expensive and I doubt Masai is willing to pay that price, especially when only one of these guys - Rondo - is a true star player.
Gettable but perhaps problematic: Brandon Jennings, Goran Dragic, Jeremy Lin, Jose Calderon, Eric Bledsoe, Grievis Vasquez. All of these guys can be traded for, but all have issues. Bledsoe will likely be VERY expensive, assuming Phoenix is willing to consider moving him (and Phoenix increasingly looks to be aiming for a speedy rebuild, so maybe not) and if he's gettable it will largely be because of an uninspiring season in Phoenix. Dragic is solid as a rock but not inspiring. Jennings has a history of selfish play and bad shot choices (like Toronto needs more of those). Jose is on a pricey contract for an aging player (and would he want to come back?). Vasquez seems more like a Jarrett Jack "best possible backup" sort of PG than a true starter.
Of these guys, I like Lin as the best option: his floor-general style of play and expertise in the pick-n-roll seems well-suited for Toronto, Landry Fields already knows how to play with him, and Houston could probably be convinced to free up his salary when they have Patrick Beverley starting at PG now. Plus, come on, it would be kind of awesome to have him here. But Lin's contract is beefy ($15m next year due to its backweighted structure) and he's had injury issues over the last year.
Rooks: Trey Burke, Michael-Carter Williams, Nemanja Nedovic, CJ McCollum, Shane Larkin, Pierre Jackson. All unproven, of course. After MCW's debut he will likely be too expensive to get. Shane Larkin has potential but is very, very raw. Burke and McCollum are injured and will miss some of the season (and will just be harder to evaluate). I really liked Jackson but he's a D-League level talent right now and needs to develop.
Next year's draft: There are really, really good PG prospects in the lottery next year. Marcus Smart, Dante Exum and Andrew Harrison are all top-10 prospects. Vasilije Micic and Jahii Carson both look to have potential if we're drafting lower (Carson is tiny at 5'10", but stupidly talented and will drop down based on his size).
So the point basically is this: if you have concerns about Kyle Lowry? It's moderately difficult to upgrade him.