Uday normally loves Devika, but the last few encounters they had ended in fights, in which she emphasized that she wasn't interested in marriage nor future nor in any doting wife-like relationships, and nor did she give him any contact info for her. This was when he complained that while his life was an open book for her, she was a total mystery - he doesn't know her last name, where she lives, works, her family, et al. This ended in a spat b/w them and she stormed off. While she parted, Uday wished that she was even remotely like Sudha.
When he discussed this w/ Jyoti & Pankaj, they suggested that he stop going to see her, and let her take the initiative the next time. So Uday stopped going to the disco and having late nights, and that's the reason that 2 nights ago, when Devika went there, there was no Uday.
In the meantime, Uday had already experienced Sudha's hospitality when she returned his shirt, duly mended, and at the Ganapati function, they seemed completely in love w/ each other. Uday now doesn't miss any opportunity to see Sudha - he treated her following her exam, and probably will for her job as well.
I think Sudha has by now slowly replaced Devika as Uday's love interest, and he's probably just waiting for Devika to break up w/ him so that he can go ahead and date Sudha.