It's only a small percent of the population, and I can only go by what I see from my own in-laws on Facebook and in person, but I sense that Sikhs are becoming wary of Modi and the BJP. At first, "anything but Congress" seemed good enough, and they were thoroughly sick of the Gandhi/Nehru families. Manmohan Singh was a nice blip, but it seemed after his tenure Congress were back to business as usual. BJP makes a lot of the fact that Hindus, Jains, and Sikhs are all part of the same faith tradition, so they are all "native" religions and not problematic. Given the other concerns, this was enough to want to give them a chance, especially partnered with a local conservative-leaning party in Punjab.
Now, after a decade of power, the bloom is off the rose (or the lotus, maybe). Modi's tendencies are more obviously authoritarian and his economic policies are very much geared towards big business and the biggest cities. Punjab is still very agrarian, and many Sikhs have been at the forefront of the farmers' protests in India. As support has eroded locally, the BJP's grip on national politics has strengthened, and you're basically seeing them re-create Khalistani terrorism out of thin air to have a scary label for frustrated farmers, mostly by going after fringe activists in India and the diaspora, in several cases carrying out extra-judicial assassinations on foreign soil.
Khalistani sympathies began a fairly quick and steep decline after Air India Flight 182 in 1985. Separatism was a relic of history in a pluralistic India, and the general sense I get is that while few Sikhs shed a tear for Indira Gandhi, it was all in the past. No one in my wife's family thought Khalistan was worth even a passing thought until Modi started turning off the entire internet in Punjab and shooting kooky uncles in Vancouver. If it becomes any sort of serious movement, it will largely be Modi's fault.
Then, with most of the "Fuck dem Muslims" items checked off the to-do list, you're beginning to see the more brazen Hindutva types start to bring out the old saw that not only is Sikhism part of the same religious tradition, it's not even distinct enough to be its own religion at all, but is just a provincial flavor of Hinduism. Devout Sikhs find this paternalistic and deeply offensive, and even less devout ones find it eye-rolling from the fringe but threatening coming from the mainstream.