JEDEC has announced that it expects to finalize the DDR5 standard by next year. It says that DDR5 will double bandwidth and density, and increase power efficiency, presumably by lowering the operating voltages again (perhaps to 1.1 V). Availability of DDR5 modules is expected by 2020:
You may have just upgraded your computer to use DDR4 recently or you may still be using DDR3, but in either case, nothing stays new forever. JEDEC, the organization in charge of defining new standards for computer memory, says that it will be demoing the next-generation DDR5 standard in June of this year and finalizing the standard sometime in 2018. DDR5 promises double the memory bandwidth and density of DDR4, and JEDEC says it will also be more power-efficient, though the organization didn't release any specific numbers or targets.
The DDR4 SDRAM specification was finalized in 2012, and DDR3 in 2007, so DDR5's arrival is to be expected (cue the Soylentils still using DDR2). One way to double the memory bandwidth of DDR5 is to double the DRAM prefetch to 16n, matching GDDR5X.
Graphics cards are beginning to ship with GDDR5X. Some graphics cards and Knights Landing Xeon Phi chips include High Bandwidth Memory (HBM). A third generation of HBM will offer increased memory bandwidth, density, and more than 8 dies in a stack. Samsung has also talked about a cheaper version of HBM for consumers with a lower total bandwidth. SPARC64 XIfx chips include Hybrid Memory Cube. GDDR6 SDRAM could raise per-pin bandwidth to 14 Gbps, from the 10-14 Gbps of GDDR5X, while lowering power consumption.
Please use GB and Gb correctly. 8 Gb = 1 GB.
I could definitely use more RAM, and as I said, there's options for when you have "too much". Even cheaper laptops are coming with 12+ GB of RAM (here's 12 GB at $330 [slickdeals.net], and this refurb has 16 GB and high specs for $700 [slickdeals.net]). Although the HDD to SSD transition is going to be more important for most users.
I will note that the cutting edge DDR4... just isn't expensive. The DRAM market has had oversupply for some time due to the decline in the PC market. Obviously, getting a new motherboard or processor is much more expensive, but if you happen to have done that, switching to DDR4 is not hard on the wallet. Some new desktops or laptops are in the $300 range and come with DDR4.
Some [anandtech.com] are predicting that memory modules will be replaced by HBM on package. Although HBM is currently more expensive, the smaller profile is well-suited for Ultrabooks or Chromebooks, even if it is not user-replaceable.