I agree with that monk; that the Buddha would teach dukkha and the way out of dukkha. It is very time-less. The forms of entertainment and sensual pleasures have changed a little, but they are very similar: sex, music, dancing, watching live theater (now it is on a screen but basically the same), participating and watching sports (the same now), indulgence in food (same now too), etc.
He might present the teachings differently. For example, to reach more people, he would most likely use the internet. I know some might find that strange, but why not? How many can you reach by preaching at the local forest or street corner versus going online with youtube videos, podcasts, etc. Of course he wouldn't be living a lavish life of a televangelist, like Joel Olsteen or one of those. He could still be a monk with simple living quarters and be online for teachings. The Buddha had wealthy donors including Anathapindika and Ambapali and I imagine in modern times a Buddha would also have wealthy donors who could foot the bills for the online costs, while the Buddha maintains perfect-sila with the Vinaya.