Of course it will get better.
The real question is whether it will get better enough, fast enough.
There's certainly a limit to how much Apple will throw (they're not going to empty out their nest-egg to fix this), and throwing money at a problem doesn't always work so well.
In particular, public-transit and in general any "non-car" data is something their maps simply don't seem to even start addressing. This isn't entirely surprising as their data provider, tomtom, is a car-nav company, but it's a huge hole, and one Apple seems to have completely missed.
One of the reasons Google's public-transit directions took so many years to get good is because teasing the necessary data out of the many different regional agencies/companies that have it is a pain-staking and slow process.
The very poor coverage in many countries is presumably because Apple's existing data providers do not have good coverage of them, so Apple probably needs to contract with region-specific providers, integrate their data (which may not be simple) with the Apple maps infrastructure etc.
All of this is doable, but it takes time, maybe years. They really needed to do a lot of this, or at least a convincing chunk of it, before the big release, not "sometime in the future."
Certainly Apple has reasons to make their own maps, but by releasing such core functionality in a form that's very clearly not ready for prime time, they've damaged their (extremely valuable) reputation as "the company that does things right."