I think 6 lanes from the Delaware Memorial Bridge to Exit 4 should be enough (and will be difficult enough to accomplish).
I think overall it won't be too tough. The Turnpike already has most of the right-of-way needed. They'll need to rebuild dozens of bridges (many of which are in need of replacing anyway) and put up sound barriers. However, expanding beyond that would be difficult. Unlike up north where they basically prepared for 12 lanes, the Turnpike down south may be able to squeeze in 8 lanes total in some distant future life, but they're not getting beyond that without major property, house and building acquisitions.
Yeah that should be enough considering I-295 is closely parallel through South Jersey and traffic would rather use the latter anyway since it’s toll-free.
You would think...except the Turnpike between 1 & 4 has congestion issues especially on summer weekends and holidays, whereas 295 doesn't.
Motorists like using the Turnpike. Most of them pay no mind to the free highway right next to it. Even coming off the Delaware Memeorial Bridge - they merge left to get on the Turnpike.