Just a word of warning though, just because the end of the cable is micro USB doesn't mean that all chargers are created equal. The actual charger needs to be able to charge at 2.1A to charge the Nexus 7 in a reasonable amount of time. Almost all phone chargers I know of charge at 1A, I think I've seen 1.2A somewhere before. So while they will provide power, it is definitely not ideal.
As for the next nexus tablet. There are always rumours about the "next" device, because there will always be the next device. will a $99 Nexus 7 come out? Maybe, maybe not. IF it does it'll be a stripped down version of what we have now to get the manufacturing costs down, or possibly discounting the current N7 to $99 when the next one is announced. But again, that's just an educated guess on my part. The only people who know are Google and whoever is building the next thing for them.
Thanks for the heads-up regarding amps needed to sufficiently charge the tablet. I do have some special adapters that are 2.1 amps that are specifically meant for higher output. One adapter is from TomTom the makers of GPS units that makes a car charger specifically for higher output of power. Plus I have another adapter from Verizon or someplace that is USB powered that is also 2.1 amps. So hopefully these adapters that put out more power will charge the tablet. I also have various USB powered batteries that output anywhere from 2,000 milliamps to 16,000 milliamps, but I have no idea if these will sufficiently charge the tablet. I'm planning on taking the tablet for weekend camping trips and I might not have electricity power, but will have USB powered batteries that will hopefully work. Plus my camper van has an auxillary battery with a 1,000 watt inverter so I can plug in small appliances for charging. I also have a couple portable solar powered battery chargers by Orange Joos and Gorilla (something?) that has a micro-USB adapter for charging devices. I know the Orange Joos solar charger can charge an iPad (or so the manufacturer claims), so I'm guessing it should also be able to charge an Android tablet as well.
I don't mind buying a $99 Nexus tablet, which would essentially make it a disposable device for my occasional usage. Otherwise, I don't mind paying a couple hundred dollars for the current Nexus 7 tablet. I do wish the Nexus 7 offers a MicroSD card slot, but alas it doesn't. An HDMI output would be nice, but not totally necessary since my Verizon Samsung Note 2 already has an HDMI outlet that I can mirror onto a television unit. As for a rear camera, that would be nice too, but I don't see myself taking many pics with a tablet. I do however take many pictures with my Note 2 phone, since the quality is quite good. I don't even do any type of video conferencing, so even the front camera is of little use for me. Storage is always the biggie, so I'm hoping the 32 GB model will last for at least some years before I run out.
As for internet access, I would use my Verizon Samsung Note 2 phone to provide internet access to the Nexus 7 tablet via the PdaNet+ and FoxFi apps installed on my phone which works great! I had already tested this at a Staples store, and had 2 tablets connected to my phone for internet access simultaneously. I'm sure I could have wirelessly tethered even more tablets, since I don't know what the limit is, but I'm guessing maybe several devices simultaneously for internet access through my phone.