Was in a very similar boat to OP until recently.
Luckily picked up a cheap PS4 Pro as I wanted to try out HDR gaming on a new huge telly – then thanks to STW hive managed to pick up a new copy of Gran Turismo for £18.
I was hugely disappointed by the last PS3 GT offering, I feared the worst when GT was reduced so quickly on the PS4.
Fear not, its excellent. It looks amazing on a big screen, and I’ve been hooked since starting playing.
Do you need to go online to play? – No. But it will expand your fun by at least 100%. The standard single player mode is great, albeit on a smaller scale then previous GT titles – but very easy to get into.
Going online is brilliant. Only downside is I sometimes have to wait up to 10mins for a match-up to be confirmed due to the seemingly pedestrian game lobby, but its worth the wait. Nothing compares to a frantic 25minute full on race in which you pip Pedro or Hanz to 3rd place on a final corner apex of perfection.
I have an old PS3 and on the very rare occassion that id fire it up I found that the online support and gameplay was no longer there (on my old titles at least).
On PS3, CoD Modern Warfare was hands down my favourite title, and I also enjoyed CoD World at War very much, so I have high hopes for CoD WWII on PS4.
I’ll eventually pick up a cheap copy of GTA too – but I have plenty of time to continue to get into Gran Turismo (and its pending expansion pack) and CoD first.
No doubt I’ll get bored and stop using it in about 6 months time, but for now at least, im finding it a great bit of kit.
In summary, your main question of ‘is the PS4 so much better?’
No, I think the gap between them is much smaller than I had hoped – but I think thats down to my Nintendo-Sega-8-bit origins and expecting a sea change on overy new console release.
The gaps are smaller now on new releases, but the difference is concentrated on home hub/media playback.
You are future proofing to a degree with a PS4, its not backwards compatible with PS3 titles though (unless playing online via PlayNow) – plus the online gaming content is going to be much better on a PS4.