Is codeigniter 3 code standards is out dated??

No I wouldn't say that. If you like how CI3 works today you can learn it and take a lot of that knowledge with you when v4 comes out.

Any framework switching between major version numbers is going to be a a little bumpy and is something you should definitely consider.

Some frameworks for example have made major version number changes year over year.
Others people think a framework that doesn't change in over a year is "dead"?

Use whatever you are most comfortable with. Is your project going to be something you know you will need to support for 5+ years and therefore a framework with a history of major version number changes may present a problem? Or is the project more of a "take the money and run" kind of thing so this won't be a problem?

As for size of application? I have some really big applications running on CodeIgniter. One reason I like it for larger applications is because it's quicker than most other frameworks out there BEFORE you even add the mountains of business logic. I would rather start with a fast framework with a small memory footprint and "build" on it than a framework that is slower and has a larger memory footprint before I even start.

If you have specific questions hopefully I or someone else here can help you.

If not try a couple of different frameworks over a weekend. Take each and spend just an hour or two max to see which one you can build a simple todo list or something in or just "get your head around"? Then just pick what "feels the best" for you. Don't worry about "Oh my they aren't using X so it can't possibly be any good"

Don Myers

https://github.com/ProjectOrangeBox / https://github.com/dmyers2004