We study the coexistence of different multicarrier waveforms such as orthogonal frequency division multiplexing (OFDM), filter-bank multicarrier (FBMC) and universal-filtered multicarrier (UFMC) waveforms in licensed shared access (LSA) for next-generation communication systems. The fundamental changes required in the existing physical layer using OFDM towards a hybrid physical layer (either OFDM-FBMC or OFDM- UFMC) ensuring backward compatibility are discussed. We also perform mutual interference analysis for the coexisting asynchronous systems sharing the LSA frequency band. Be- cause of the non-orthogonality between their respective transmit signals, power is spilled from a system to the other causing interference. In consideration of analyzing this interaction, power spectral densities of the multicarrier waveforms are exploited. We quantify the amount of percentage power-loss experienced by the interfering systems for not fully exploiting their available power budgets. The simulation results reveal that the interfering system with FBMC suffers the least percentage power-power loss due to its very low side-lobes while conventional OFDM-based system suffers the most. The UFMC-based system exhibits intermediary performance with respect to achieved throughput and power-loss when compared with OFDM and FBMC-based systems.