TelloFpv was developed in native Android java and there is absolutly no way of "porting" it to IOS. It would be a complete re-write from scratch in a different language. From a business perspective I should have done that earlier this year instead of spending time on failed experiments like FollowMe and vGPS but thats hindsight.
As stated before the Android version was driven by a personal need - not revenue. The IOS version on the other hand has to be driven by revenue (I am no IOS user and don't have a personal need for such an app).
Some thoughs on this...
The global mobile market is around 75% Android and 25% IOS. But that doesn't say much about the distribution of the OS amoungs
Tello users.
Android phones on average are way cheaper than Iphones. So there is a tendency that IOS market shares are much lower in poor countries than in developed rich countries. Apple has a <5% market share in some low-income countries - but a 55% share in the US for example.
A drone (even little
Tello) is luxury thing and very few are sold in Bangladesh or Botswana. The vast majority are sold in US, Canada and Central Europe. This is also where Apple's market share is much bigger than the global market share of 25% suggests.
And don't forget: Apple stores sell DJI drones including
Tello. So its reasonable to assume that this distribution channel helps selling to Apple users.
Its really hard to guess how many
Tello users are on IOS vs Android. I have seen polls on Facebook suggesting its about 50% IOS and 50% Andoid but the sample set is pretty small.
If these figures are correct an additional IOS version released a year ago would have been smart. But now?
The current situation is a bit different. We are about a year later in the product lifecycle compared to when TelloFpv was introduced.
Tello is now very old and should have been replaced long ago. I guess nobody at Ryze / DJI expected such a long production run. Its still a drone without true competition but nobody could have guessed that at the release date.
Over the last year the app had a pretty good run and generated enough revenue to be "worth" the effort, but sales have been dropping sharply for the last 2-3 months. Some of this is caused by the appearance of a pirated APK that was cracked by a user of this forum

- but I guess
Tello's time is just slowly coming to an end.
A newly introduced IOS version would not have the time to generate similar revenue and simply won't pay off anymore. Too late
That said I started work on a new app that targets both Android and IOS. The app will not become a replacement for TelloFpv, its a completely different thing: much simpler, much smaller feature set, but portable to IOS. No clue if it will ever leave the workbench at all - right now its only a personal experiment and playground.