Obsolescence management is as much art as science (sometimes I wish there really was a crystal ball available).
Is it true that DIP chips and ICs are going to be obsolete in the near
At the risk of trying to see into the future by looking at past and current trends, I really don't think so; existing parts may slowly drop DIP packaging but it ...
No, there aren't. If nothing else, it would be a security nightmare for anyone who used serial comms to connect to other systems.
Exception: Some systems allow you to use the serial port as the "console". If that's the case, then you get access to a command prompt, at which you can enter any command you like.
de is an assembler directive to declare an EEPROM data byte. org is also a directive.
You can find a full list of assembler directives in the MPASM manual (see 4.17 for de).
In general all assemblers will have directives of this kind, that don't map to machine language instructions, but the syntax varies between assemblers.