Nope we don't need to redevelop everything this time. The time period won't be more since ADA is already working on AMCA . Tedbf seems to be slightly modified twin engine Tejas just like Mirage 4000 concept .
5-6 years will be enough to get it done.
Exactly it's parallel development. Mwf , tedbf/orca , amca will share a lot . From radar to ew components to weapons and even lot of lrus ( smaller internal once ).
That is the benefit of lca program . We now have an ecosystem of Indian products .
Uttam radar , astra missile family , displays , fuel tanks, maws , digital rwr , secure sdr , Indian pods ,
Internal spj, senor fusion etc.
Once you have basic components in place outer platform is not that difficult to build unless it's stealth which is a different game.
In next 7-8 years we will not only deliver mwf to iaf but also tedbf will be flying and reaching ioc . Beside amca and aura both will be flying in advance prototypes.
Just wait and watch and explosion of Indian aerospace is coming.