Without some very, very serious socio-demographic altering (and by this I mean systematic genocide/deportation), it is highly unlikely Sikhism would replace Hinduism as the dominant religion in India.
A more expansive Sikh Empire would definitely increase the opportunity for Sikh converts to remain stable through parts of Northern India and it would form a powerful religious undercurrent that would at least influence people who practice many of the variations for Hinduism. A Sikh successor state to the Mughals for even a few decades would have a large religious impact on much of India, though I don't think in most scenarios mass conversions or anything of the sort are likely.
Nonetheless, Sikhism could become more prominent in Northern India, particularly in the areas historically controlled by the Sikhs such as otl Delhi, West and East Punjab, Kashmir and Jammu, Haryana, portions of Western Uttar Pradesh and portions of northern Rajisthan... perhaps even Uttarakhand or Himachal Pradesh in a very optimistic scenario.