For one thing, there are only four products that overlap between the two companies. . .
Macromedia Fireworks versus Adobe Photoshop = A no-brainer. Photoshop is way more capable than Fireworks and is the industry standard. Fireworks won't be relegated to "Baby Photoshop" because Adobe already sells baby photoshop. Fireworks will go byebye and Adobe will offer existing users a discount on an upgrade to Photoshop.
Macromedia Freehand versus Adobe Illustrator = Also a no-brainer. While the products aren't as unbalanced features-wise as Photoshop/Fireworks, Illustrator's the industry standard and Freehand is a niche product. Freehand will go byebye and Adobe will offer existing users a discount on an upgrade to Illustrator.
Macromedia Dreamweaver versus Adobe GoLive = Also a no-brainer, but in the opposite direction. GoLive's days were numbered anyway, as Adobe had plans to make a new web-editing product that'd surpass everything else in the market (see: InDesign). GoLive will go byebye. If Adobe continues making a new market-leader, it'll be branded with the Dreamweaver name so it'll leverage the product's market.
Macromedia FlashPaper versus Adobe Acrobat = Also a no-brainer. Acrobat will survive, obviously. Whether it'll be given the ability to genrate Flash content in addition to Acrobat content remains to be seen, but I'm doubtful. Flash-based print-documents, while interesting, weren't taking any market-share from Acrobat.
When I say "going byebye", I don't yet know if that means that the product will be sold or if the products will be allowed to fade away, like PageMaker and FrameMaker. I suppose it'd depend if there was an eager buyer for 'em, and I can't imagine that there'd be anyone eager to spend much money on 'em.
The only place I think things will get interesting will be in the Flash versus SVG arena. Adobe was a big SVG proponent, but now they own the product that's SVG's most obvious "spoiler". Given that I don't see SVG content taking any market-share from Flash anytime soon, I expect that Adobe will start de-emphasizing SVG in favor of SWF. Given that there are now several products that can create content for Flash's SWF format, I don't think that Flash is viewed as such a closed box anymore that demands an fully open competitor.
Rumor has it that product brands will be unchanged, so Flash will still be Flash, Dreamweaver will still be Dreamweaver, etc. That doesn't surprise me, as the products' brand names are fairly compatible with each other.
Personally, I'm excited by the change. Adobe is a good company that makes good products. Their developer support is excellent (remember, these were the folks who pretty-much invented the plug in market with the Photoshop Plug-In) and they make a good product. The products will likely get a lot more integration, like giving Adobe's Video editing products the ability to create video content that'll go directly into Flash, making the desktop publishing and web publishing products more compatible, etc.
Macromedia also makes a good product, but they concentrate too hard on adding "bleeding edge" features on a one-year cycle and stability is becoming a problem. Hopefully an injection of talent and cash can make their stuff even better.