I'm pretty sure crossovers will still happen but I'm assuming we're supposed to treat it like lightyears. It'll be like character's are traveling from one planet to the next. They think they're going at normal speed but they won't realize how much time has actually passed. So while Preeta's engagement was happening Pragya risked actual jail time and possible death to free Abhi, Daadi died, abhigya separated, Pragya tried to kill herself (based on spoilers), Sarla must have sent her to England (because sending Pragz far away was what she tried to do during Abhi's memory loss. So it only makes sense that she'd do the same). Pragya gives birth. Said child is now 6 years old. And all the while on planet Kundali only 5 minutes have passed while planet Kumkum ate through 7 years. It's all okay though. Planet Kumkum will probably be frozen in time for the next 2 years. So planet Kundali has plenty of time to catch up.
Sidenote: 2 years ago a character (he was a teen at the time) came to KKB to promote his show. Pragya was kidnapped for the 54th time. Said character helped Abhi save her. Then the following year THE SAME character returns only this time he's the same age as Abhigya. He comes to Mehr mansion looking for his wife -- only to find out his biwi has hoped on a train and is headed to A PERIOD show that took place in the 1930s. I sh!# you not.
So turn off your brain and just go with the flow. It's the healthier option.