A healthy opposition is in great interest of Democracy, it prevent complacency and keeps government in check.
That bit said, while it is true that Congress is the only party having pan Indian presence that can challenge BJP, the fact remains that the current leadership in Congress honestly doesn't give much hope.
After last year defeat in LS elections, a lot of experts pointed out that the congress top brass and leadership had almost lost any kind of connect with local masses and the communication of behalf of leaders with grass root and the representation of common people was all but finished.
Today what Congress requires is a person to lead a party that has acceptance based on his vision. unfortunately the President designate has been playing a catching game with PM Modi, which is going to do little good. Everytime he goes after PM, he is made to look ridicule and childish.
Its time they realize that the only way to win people heart and votes is by projecting solution to their problems and connecting with them. I'm afraid this part is still missing.
if Congress needs to find its Mojo, it won't be a bad idea to try and hand command to a Non Gandhi young leader (may be in a region first). but i don't see it happening anytime soon.