I've just discovered that MSP430FR5994 is a true 20 bit MCU in meaning that it has 20-bit wide CPU, 20-bit wide address bus and 20-bit data bus. The same thing with DMA. (And, of course, 32-bit LEA with dedicated 32-bit data bus, which is already known).
This is just a good news.
Just hope to have MSP430FR5994 RTM with integrated at least 32-bit BIN-to-BCD converter to properly convert 20-bit decimal numbers to 32-bit BCD.