True Strike: The extra duration improves this originally difficult to use cantrip. Thumbs up!
True Strike is bad. No two ways about it. Even being able to hold it for a turn before discharging it does not fix the fact that you are choosing to spend one action to improve a second action by a lesser amount than simply taking the action twice would.
Example: You have a 65% chance to hit. With True Strike this increases to a 100% chance to hit. Not sure the actual number.
Or you could attack twice at 65% chance to hit. This gives you a +65% chance of damaging your target (compared to True Strike's +45%). The only possible use for True Strike is if for whatever reason you can't get line of sight to the target this turn, but will be able to next turn. This is so insanely situational that you're better off picking up a second damage cantrip because you're more likely to run into an enemy that resists fire than you are a battlefield that offers 100% concealment across a whole 30 ft move.
Sometimes guaranteeing a hit is better than chancing it because of situations, and right now it works really well with classes that have multi attacks or action surges.