I will reply to both
@MagicalPhantom345 &
@123456789blaaa here since their points are interlinked.
@123456789blaaa
Madhava Rao died of tuberculosis when he was in his 20s. Let us hypothetically grant him a life till 70. In fact, in the aftermath of Panipat, he was busy putting down all challenges to his throne. It was only by the late 1760s that he secured the upper hand, but then he died in 1772, IIRC. He already had made Haidar his primary target. His invasion of Srirangapattanam had Haidar agreeing to a humiliating peace after a disastrous defeat at Chinakurali. If he lives long, he is likely to do what the British did, but with a twist. He would remove Haidar restoring the old Hindu dynasty (less likely) or compelling Haidar into an alliance with Haidar agreeing to pay chauth & he was also keen on recovering the Maratha possessions in the Carnatic. By the time he died, he had regained the old Tungabhadra borders for the Marathas. Assuming that the Second Mysore War (& war with the British) occurs some time in the 1770s or 1780s, the British & Madhava Rao come into conflict. In this event, Mysore might side with the British. (neither Tipu, nor Haidar would consent to playing second fiddle to either Madhava Rao or the British), in this war, or at least play a waiting game to see who would come out on top in the Maratha-British conflict to join the winners. The next step would be determined by the outcome of this Maratha-British conflict. If it goes in favour of the Marathas, it would mean that the British would be forced to release Awadh as a fully independent state allied to the Marathas & forced to retreat to Bihar & Bengal. In the south, the British would be forced to give up their alliance with Travancore hand over the old Carnatic fortresses to the Marathas & be reduced to the Fort of Madras. Bombay would be given up or at least demilitarised. Northern Circars would be returned to the Nizam of Hyderabad. It is hard to envision the Marathas so successful that they would be able to overthrow the British power in Bengal itself. However, after Madhava Rao died, it would be back to square one for the British.
@MagicalPhantom345
It is hard for Mysore to retain her old Krishna borders because the Tungabhadra was considered the natural border between the Marathas & Mysore. What you are envisioning requires 3 things to happen.
a) Both the Marathas & Mysore are very successful in Second Mysore/First Maratha wars (not likely). Mysore, despite being a secondary theatre for the British here, didn't do all that well against the British. Only devastating success would induce the British to give up entire Carnatic, which is what is required for the British to be completely ousted from the Carnatic. The best they can hope to achieve is get what Haidar Ali was fighting for - control of Thiruchirappally & Madurai, maybe de facto suzerainty over Thanjavur. This would isolate the Travancore Raja & he might be compelled to do what the Cochin Raja did - acknowledge Haidar/Tipu supremacy.
b) As mentioned previously, if both Marathas & Mysore are very successful, it would also break the Maratha-Mysore alliance. They would immediately turn on each other, with the Marathas invading Mysore. If that happened, the Marathas are more likely to win, especially as they are coming in flush from a victory over the British. For Mysore to retain its Krishna borders, they have to win the war against the Marathas, or at least fight them to a draw. (not likely again).
c) It requires the British to be eventually eliminated from India totally by 1820s at least. The British would never allow a reasonably strong Indian power, especially one that has fought wars with them, to control the sea coast. Travancore was the biggest state that controlled the sea coast. If Haidar/Tipu/their successors control the sea coast, they would have to be reduced to Travancore levels of power. That means no Krishna border, no Travancore & no sea coast. The British never allowed the less hostile Hyderabad Nizam to control the sea coast. So the best outcome that for Tipu/his successors in the event of British success would be to have the territory that Mysore did (maybe some more like Salem, Dindigal, Bellary, etc).