Bolivia is left disappointed by the uselessness of its newly acquired territory. Both are even more comprehensively wrecked than they were in OTL, given the scale of the sacrifice both had made. For Bolivia to win, it requires more manpower, more casualties, and more debt.
Expect a severely revanchist Paraguay which aligns itself with 'anybody willing to put one up Bolivia'. Given a comprehensive enough Bolivian victory, the two countries would possibly end up glowering at eachother over the River Paraguay. It would require further massive investment by Bolivia to make a) the Chaco defensible and b) bring enough settlers into the Chaco to meaningfully occupy it. Any future war will be hugely in a militarised Paraguay's favour, given that the Paraguayan population centres are directly across the river, while Bolivia would still have to transport troops from the Andes.
On the other hand, Bolivia would have a theoretical outlet to the sea down the River Paraguay (Huzzah! cry the Bolivians), which may work in its favour in terms of trade and accessibility. There are already transport routes across the region, which will have been developed during the war. So, potentially, a trade boom for Bolivia if it can hold the territory in question.
Frankly, though, the most optimistic outcome for the Bolivians is a partition of the Chaco somewhere nearer the middle. Bear in mind, the Paraguayans have (and will) fight tenaciously: if history is anything to go by, the Paraguayan population doesn't do war by half. Most likely, the two exhausted sides agree to a partition that gives each something out of the fight, and possibly direct Bolivian access to the River Paraguay in the north into the bargain.