I don't know about the statement that columns for UPLC are "not that much developed now". Waters alone is offering 10 column chemistries on two different base particles. There are several other companies that have developed sub-2-micron particles. That does not make it 1000 different C18s, as in classical HPLC, but you have plenty of options at your disposal.
What you need to consider is a completely different story. UPLC columns give you high resolution in a shorter time than classical columns. This means that your peaks are narrower, and your MS system needs to be faster to be able to deal with narrow peaks to take advantage of the UPLC technology. If your MS system is not fast enough, the purchase of a UPLC system does not give you an advantage. If the MS system is fast, the use of UPLC columns with a UPLC system will give you higher resolution, less interference, often resulting in less ion suppression, and overall the opportunity to do a faster analysis.