Wang Ling has an interesting proposal to improve the iOS keyboard experience for international users who frequently switch between keyboards:
If you are a monolingual user you are unlikely to feel the need of a separate group of occasionally-used keyboard. Most of you enable at most two keyboards, your language keyboard and Emoji keyboard. Switching between two keyboards is never an issue because it never incurs unnecessary inconvenience. You always switch to your target keyboard directly and immediately.
However, if you are a multilingual user like me or many other Chinese (I guess also many other English-as-second-language users) users, things are very different. We use both Chinese and English keyboards. We type mixture of Chinese and English very often so we need to switch between the two frequently. If Chinese and English are the only keyboard we use there will be no issues, as explained above. But Emoji is fun and we also want to use it, occasionally.
Replace "Chinese" with "Italian", and that's me. Every day, I'm constantly switching between the Italian and US English keyboards on my iOS devices and the experience is slow and annoying. Once you throw in a couple of additional keyboards in the mix (I use Emoji and Copied) the only sensible way to switch keyboards is tapping & holding the globe button then sliding over to the keyboard you want to use again – which takes about 1 second in my experience. That doesn't sound like a lot, but the annoyance adds up; plus, imagine doing that for years. Assuming I switch between English and Italian keyboards 50 times a day (and I'm lowballing here), I can say I lose about 5 hours/year to this keyboard switching dance on iOS.
This won't seem like a big deal to monolingual users, but trust me – it's one of the most tedious aspects of working and communicating with others on iOS.
I see two possible solutions: either Apple implements something close to Ling's idea with separate shortcuts for frequent and occasional keyboards, or, even better, they build a smarter, unified keyboard that automatically recognizes multiple languages at a time (though that obviously wouldn't work for Chinese and other non-QWERTY keyboards).