This post has been marked by the post author as the answer.
Summary (in case TGC ever consider to read this topic)
Subject: Release GameGuru as an addon or asset pack for Unreal Engine.
Question: Would you be interested?
Pros (in general not only compared to GameGuru):
-reliable and stable architecture
-each version of Unreal comes wit it own EULA (safe for long term plans)
-no need to develop the engine but game mechanics (less work for TGC)
-paid priority support available (if you ever need a fix ASAP you can pay Epic to make it a priority to avoid any delays)
-advanced rendering
-optimization (better performance)
-compress and encrypt assets in release build
-cross platform (VR and AR ready)
-open-source (C++) (anything broken you can fix it then contribute back to help everyone)
-no paid version (Unreal)
-no monthly subscription (Unreal)
-free with no limitations (Unreal)
-easy scripting (Blueprint)
-easy drag 'n drop workflow of GameGuru can be maintained in Unreal with Blueprint Assets
-no need to rewrite everything in Blueprint, can be also written in C++
-the Epic Store provide lots of very high quality assets including many free assets
Advanced features included out of the box in Unreal:
-destructible environment
-vehicle physics
-cloth, hear, liquid simulation
-particle physics (create realistic smoke and dust effects)
-advanced terrain and foliage editing tools.
-mesh manipulation and creation tools.
-3D UI Widgets (to create 3D terminals and console screens that we can interact with)
-integration with 3rd party tools and services like Mixamo, Megascans, Substance Painter, Steam, SpatialOS and Epic Online Service
Cons (based on user feedback in this topic):
-people with ongoing projects can not afford to switch to a new engine
-require to pay 5% royalty over $3k revenue in a quarter (it is not for TGC but for users, engine would cost nothing for TGC)
-would be not compatible with the current version of GameGuru
-lose Lua support
Other concerns raised by the community:
-would require to start from scratch
-would replace GameGuru that everyone love
-being based on a 3rd party engine and architecture means less control for TGC
-some GameGuru assets are not acceptable quality to be published in the Epic Store (no need to publish in Epic store)
Community opinion (based on feedback):
Most people seems to be not interested in Unreal, don't believe it is necessary or logical to build something like GameGuru on top of Unreal. Others are simply loyal to the direction GameGuru is going as a stand alone, independent product, prefer to stay this way and willing to support it whatever direction TGC is taking it.
Personal opinion:
I believe most people here are against this idea and won't support it primarily because they don't know Unreal, they have false information and they are worried it would be more complicated to use. Others may have put lot of time and effort in to their GG project and can not afford to start from scratch in a new engine and would prefer to see GG being developed further. Content creators may dislike the idea because they have released many assets for GameGuru and they can not afford to update their content for Unreal. The Epic Store would also mean more competitor for content creators and better quality assets to compete against meaning more work they need to put in to their assets to be competitive.
In my opinion it would be logical to make a product like GameGuru on top of Unreal for the same benefits GameGuru has to offer targeting the same audience and also for the benefits Unreal has to offer to target new audience and to fit commercial and professional use better. In my opinion GameGuru and Unreal combined could be a very powerful tool for beginners, students and even professionals.
I have replied to most concerns and cons, and shared more details in this topic, please read all my previous replies.
Since, a moderator decided to mark this topic as "Solved" without consulting with me first and the reply was marked as Answer by the moderator was not satisfying because contained lot of false information about Unreal, I decided it is better to write this summary and mark this as the Answer before a moderator close this topic and consider it solved without consulting with me.
Thank you to everyone who participated and shared your opinions.