TLDR; don't worry, be happy.
First off, there are always negative things people say about anything. PHP itself is viewed by many as abomination. It's slow, it doesn't scale, blaa blaa, you name it.
Development is very fast moving industry, and it's very easy to become overwhelmed with all the options and trying to figure out what's the "right" technology to learn and work with.
IMHO, your main goal is to keep your clients happy, regardless what technology you use.
Does the tech deliver what they want with your technology stack?
Are you able to implement it quick enough with features in the framework or your own existing set of plugins?
If you can answer yes to these questions (which I see you did in OP saying your clients are happy), you probably can put less stress on yourself, life is hard as it is.
Learn new things, by all means, but you really need to look changing things around if you have problem delivering results, not because "hey, new fancy tech is here, lets spend next 6 months rewriting everything!".
While Laravel might come with a lot of features built in opinionated way, but if you are still quicker doing the work in CodeIgniter, it makes sense to keep using what you're good at.
One thing you have to take account with Laravel is that the guys building it actually make all their living on side products and conferences, so they have time and energy to push their framework, and CI is no match in marketing department, even when it's actually better framework (in my opinion) for many many cases. Just see how defensive Laravel guys get about performance
Back to CI, I suspect you might find v4 structure slightly more modern than v3 with all the namespacing and autoloading and all, but again, v3 isn't just going to stop working, because v4 came out.
I personally want and will move to v4 as soon as possible, because it has quite few features built in I've had to add on top of v3 myself, but that's not to say that every developer will find upgrade beneficial right away.
Hope you'll find your spark again.
