This sounds a little tiresome, but considering how they are doing a remake of FF-VII with awesome improved graphics, do you think they will make remakes of all Kingdom Hearts' previous games with KH-III's graphics? The original graphics were great, but the new ones could make the games even better. Only problem I see is that I don't want to play a version of the original KH where they have to removed Tarzan's world. 

I very much doubt it. Kingdom Hearts is in a different place than FFVII. The VII remake was almost needed & guaranteed to happen, since it's one of their most popular & fondly remembered games ever. It was also a text-based adventure & a turn-based RPG made in 1997. Yes, they've remastered the game into HD & rereleased it on many platforms, but not without their difficulties.

Kingdom Hearts is a completely different story. Sure, they could make graphically-enhanced remakes of the games, but they're not liable to. Doing so would not only be time & labor-intensive, but also cost-effective. There's 9 games before III & if they were to only remake the 6 that got ported in the HD collections, it'd be pretty expensive. The only benefits to doing so would be the graphical upgrades &, hopefully, they could fix a lot of the problems with the games before & after II, like KHI being very stiff & awkward to control (also a better way to get the Ultima Weapon), Chain of Memories being repetitive, RNG-led garbage, Birth By Sleep needing better physical combos, proper stagger on enemies, a revenge counter, & balance fixes, & Dream Drop Distance needing the same things as BBS. Maybe they could also do rerecordings of Terra & Aqua's dialogue in the BBS dub since they're pretty bad due to poor direction & their VAs being new to voice acting at the time & being a LOT better in III & having a voice double rerecord Sora's dialogue in Re:Chain because Haley Joel Osment sounded exactly like he did in II for that dub & Sora's supposed to be the same age he was in the first game, which was already shown in the original game when they reused his voice clips from the first game. Also, maybe they could get around to porting the remakes to other platforms like they should've already with the HD remasters.

But, that's the thing, they already have the HD collections. They have the definitive editions of the games on consoles that everyone can easily buy. FFVII is a game that Square knows they can take the gamble on, since they've produced a lot of sequels, merch, & whatnot on, so it makes more sense to do the remake there. I hope I made sense here.

Kingdom Hearts would never get something on the scale of FF7 Remake, it's a special case

 

The biggest hurdle is Deep Jungle. I think the main reason they didn't get a full remake is because they couldn't get the rights to Remake deep Jungle, but they were able to remaster it through a loophole. To remake it up to KH3's quality, they'd need to acquire the rights again, which aren't being given out. They'd have to drop Deep Jungle and find a replacement world to remake it, and that would change the story and upset fans. If the owners of Tarzan are willing to play ball one day, they might consider remaking the games. They can't just leave KH1 and remake everything else, so their hands are tied on the matter.

It's possible the DS games might get a full remake at some point, with polished graphics and tuned gameplay, as well as a console port of Union Cross. However the other games are fully 3D and in very playable condition for modern gamers, unlike Final Fantasy VII.